Man found guilty in 1975 cold-case killing in Richmond Beach

A King County jury today found a man guilty of second-degree murder in a cold-case slaying from 1975.

James Groth, 50, was a suspect in the slaying of 16-year-old Diana "Dinah" Peterson since shortly after her body was found in the yard of her family's Richmond Beach home.

Over the years, the King County Sheriff's Office investigated two people in the Valentine's Day slaying: Peterson's then-19-year-old boyfriend and Groth, who was the victim's 16-year-old neighbor at the time. While both have been investigated in the fatal stabbing -- decades apart -- only Groth was charged.

Groth and Peterson were classmates at the former Shoreline High School. Investigators say he was infatuated with her and was often at the Peterson home.

On the night of Feb. 14, 1975, Peterson, a friend and Groth were watching television in the basement of the Peterson home. Peterson's mother agreed to let her daughter go with other friends to a nearby pizza parlor as long as she returned by 10:30 p.m. Groth stayed behind.

George Peterson found her daughter's body the next morning.

Groth, a former fisherman, was charged with first-degree murder in December 2007.